Multifunction printers include a printing apparatus for the printing of documents, as well as a scanning apparatus for scanning or copying documents or other objects. A conventional optical scanning apparatus includes a transparent platen for holding the item to be scanned. A lid covers the platen when not in use, as well as during the scanning process in order to prevent excessive stray light from entering the optical sensor array.
Optical scanners operate by imaging an object (e.g. a document) with a light source, and sensing a resultant light signal with an optical sensor array. Each optical sensor or photoreceptor in the array (typically a linear array) produces a data signal representative of the intensity of light impinged thereon for a corresponding portion of the imaged object. The data signals from the array of sensors are then processed (typically digitized) and stored in a temporary memory such as a semiconductor memory or on a hard disk of a computer, for example, for subsequent manipulation and printing or display, such as on a computer monitor. The image of the scanned object is projected onto the optical photo sensor array incrementally by use of a moving scan line. The moving scan line is produced either by moving the document with respect to the scan bar assembly that includes the array of optical sensors, or by moving the scan bar assembly relative to the document.
A common type of scanner uses a contact image sensor (CIS) scan bar. A CIS scan bar includes a contact image sensor scan element having a length that is substantially equal to the width of the scanning region. The photoreceptors in a CIS are substantially the same size as the pixel resolution of the scanner. The CIS has a short depth of field and is typically mounted beneath the transparent platen upon which the document is placed. A scan bar assembly includes the CIS scan element, as well as gears for power transmission to move the scan bar assembly. One or more roller spacers in the CIS scan bar assembly are biased against the bottom of the scanner glass so that the CIS scan element is always at substantially the same distance from the top of the transparent platen.
In a conventional multifunction printer, the transparent platen is recessed within a frame, such that when the lid is closed, the lid typically contacts the top of the frame rather than the top of the transparent platen. Typically, attached to the lid is a white reflective backing plate that protrudes into the recess to hold the original to be scanned flat against the top of the transparent platen. Thus, the recessing of the transparent platen below the top of the frame requires an additional part as well as additional height of the multifunction printer. In addition, in some instances a user desires to scan or copy a portion of a document that extends beyond the recess. It can be difficult to position such a document without creasing it or moving it when the lid closes over it and the backing plate pushes part of the document down against the transparent platen, while another part of the document extends beyond the recess over the frame.
What is needed is a multifunction printer with a scanning apparatus having a reduced overall height, fewer parts, and the ability to more readily scan oversized documents. Additionally, an aesthetically pleasing appearance of the scanning apparatus that distinguishes the multifunction printer from conventional multifunction printers can also be advantageous.